Remove IntegrationKit CRD

### Requirement

In order to simplify the building system we should remove the CRD. A side effect would be the removal of incremental kits, but the simplification and the possibility to directly leverage the Build the same way we do for self managed Integrations is a great tradeoff to consider.

Start by locating the IntegrationKit CRD and tracing the build-system paths that depend on it, especially incremental kits and self-managed Integrations. Confirm the impact of removing the CRD and define done as a simplified build flow that preserves the intended direct Build behavior; the payload names no files or tests.

Written by the indexing model from the issue text.